Given an array arr[] and a position in array, k. Write a function name reverse (a[], k) such that it reverses subarray arr[0..k-1]. Extra space used should be O(1) and time complexity should be O(k).
Examples:
Input: arr[] = {1, 2, 3, 4, 5, 6}
k = 4
Output: arr[] = {4, 3, 2, 1, 5, 6}
This problem has existing solution please refer Reverse an array upto a given position link. We will solve this problem quickly in Python.
# Program to Reverse an array # upto a given position def reverseArrayUptoK(input, k): # reverse list starting from k-1 position # and split remaining list after k # concat both parts and print # input[k-1::-1] --> generate list starting # from k-1 position element till first # element in reverse order print (input[k-1::-1] + input[k:]) # Driver program if __name__ == "__main__": input = [1, 2, 3, 4, 5, 6] k = 4 reverseArrayUptoK(input, k) |
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Output:
[4, 3, 2, 1, 5, 6]
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